Cellulose derivative composition



Patented Feb. 6, 1 40 UNITED STATES ,r 2,189,333 PATENT OFFICE .CELLULOSE' DERIVATIVE. ooMrosrrro Shailer L. Bass and Edgar C. Britten, Midland,

,MiClL, assignors to The Dow Chemical. Company, Midland, Mich., a corporation of Michigan No Drawing. Application December 27, 1938,

r Serial No. 247,832 I invention relat s to cellulose derivative compositions, and particularly to compositions plasticized with certain poly-halogenated diphenyloxide derivatives.

, Most of the plasticizers employed in cellulose derivative compositionssoften the cellulose derivative, while at the same time modifying its flexibility and extensibility. When it is desired to produce a molding plastic from a cellulose derivativegone of the; common plasticizers is added to the said derivative in sufficient quan tity to produce the desired degree of plastic flow at moderate molding temperatures. The desired plastic properties in the composition are usually v attained at the expense of the hardness of the product at room temperature since the softening effect" of most plasticizers is the most noticeable property contributed to thecomposition.

It is highly desirable that a plasticizer have low volatility so that it will not evaporate from the plasticized composition on aging or at molding temperatures; it should be resistant to attack by water, acids and alkali; insoluble in oils and greases; resistant to discoloration and exposure to. sunlight; and compositions con taining the plasticizer should ,remain'flexible at low temperatures. Few, if any, of the known plasticizers contribute all of the desired propat moderate pressures and temperatures.

erties to cellulose derivative compositions and most of the heretofore known plasticizers fail entirely to provide cellulose derivative compositions wherein the cellulose derivative retains most of its hardness while at the same time undergoing an increase in toughness, flexibility, and dielectric properties. i A plasticizer which would produce an increase in toughness and flexibility without unduly softening the cellulose j derivative is much to be desired.

Ethyl cellulose has recently become of com-- mercial importance in the preparation ofplastics and coating compositions. This cellulose derivative is inherently softer, tougher, and more extensible than the cellulose esters such as nitrocellulose and cellulose acetate. Ethyl cellulose is, also more generally compatible with the cus tomary plasticizers than are the other cellulose ethers of cellulose. The problem of plasticizlng benzyl cellulose is similar to that of ethyl cellu- 5"Claims.- 01. 106-40 e lose but is made. more difficult because of the inherently greater'softness of benzyl cellulose and the tendency of the latter to be softened and weakened by the addition of. even small quantities of the usual plasticizers.

It must beremembered that the: hardness;- toughness, and extensibility desired in cellulose.

derivative compositions is largely determined by the use to which such compositions may be put.

Plastics for injection molding mustflow well at molding temperatures but should harden rapidly at lower temperatures.

They should be hard enough when cold to withstand scratching, and

tough enough to withstand shock. Plastics for extrusion coating of wire, for example, must flow well, have high flexibility at all temperatures met with in service, andbesufiiciently hard and tough to withstand abrasion. In addition, the

composition must provide good electrical insulation. Similarly, lacquer coatings must be hard, tough, and possess elastic extensibility to prevent cracking. In addition, retention of flexibillty on exposure to .lightand heat is desirable.

Fabric coatings should be. flexible, hard, glossy,

and free from tackiness and beresistant to dis coloration by alkalies and detergents.

It is accordingly an object of the pres ent invention to provide cellulose. derivative compositions comprisinga plasticizer which increases the toughness and flexibility of thecellulose derivative withoutunduly softening the same. It is'another object of the invention to provide rivatives and such plasticizerswhich have good strength characteristics and which are nearly as hard andin many instances harder thanthe cellulose derivative alone. It is a further ob ject of the invention to provide cellulose derivative plastics having good flow characteristics,

met with in service, and sufficient hardness and high degree of flexibility at all temperatures toughnesstowithstand abrasion. It is a furnew plastic compositionacomprising cellulose d e-'v 1 ther object to provide such a composition having good electrical insulation properties. It is another object of the invention to provide such compositions which are flexible, hard, glossy, free from tackiness, and resistant to discoloration by alkalies and detergents,or on exposure to light. Other objects of the invention will become apparent as the description proceeds.

related objects may be attained in a cellulose derivative composition plasticized with one or a combination of polybrominated diaryl ethers having the formula According to theinvention, the foregoingand wherein Yis a member of the class consisting of the phenyl group. and hydrogen, Xis at least one of the halogens,chlorine and bromine, and n is a numeral from 1 to 3. compositions contain varying amounts of the plasticizer depending on the use of requirements; I Thus, molding plastics contain from to 40 parts of a plasticizer conforming to the foregoing general formula, per 100 parts of the cellulose derivative. Wire coating compositions, and those forthe extrusion of flexible tubing, may contain up to about 100 parts of plasticizer per 100 parts of the cellulose derivative. Lacquer coatings may contain up to 100 partsor more of plasticizer per 100 parts of the. cellulose derivative.

, Compounds falling under the foregoing general formula will contain at least 4 and as many see halogen atoms. Of the possible 6 halogen atoms at least 3 are always bromine and not more than} may be chlorine. The aryl ethers from which the halogenated products are prepared are ph enyl ether (diphenyloxide) and phenyl-diphenyl ether. Examples of the compounds which we have found useful for the present purpose include tribromo-mono-chlorodiphenyloxide, tribromo-dichloro-diphenyloxide, pentabromo-mono-chloro-diphenyloxide, tetra loromo dichloro diphenyloxide, hexabromo-diphenyloxide, dibromo-phenyl-diphenyloxide, penrather than pure individual compounds.

' tabrommmOno-chloro-phenyl-diphenyloxide, and

hexabromo-phenyldiphenyloxide. In most instances the materials employed are a mixture of isomers or of adjacent substitution products The average analysis in each'case was such as to conform to the general formula given above. The desired properties are found to be contributed to cellulose derivative compositions only when the poly-halogenated diphenyloxide derivatives contain at least 4 halogen atoms of which at least 3 are bromine. The lower halogenated derivatives and those containing more chlorine than bromine were found to fall within the general class which we may refer to here as softening plasticizers for the cellulose derivatives in contradictinction to the group with which we are here concerned and which we may designate as hardening plasticizers. I

The poly-halogenated diphenyloxide deriva- The preferred 5 e 1 tives with which the invention is concerned impart to cellulose derivativecompositions an unusual combination of the desirable qualities of extensibility, hardness, toughness, and electrical insulation. In general. cellulose derivative compositions'consisting of 15 parts of one or more of the new plasticizers for each 100 parts of cellulose derivative, exhibits a hardness index of at least 90. The, hardness index of a oelluloscderivative composition is the hardness of that composition reported in terms of the percent relationbetween the said hardness and that of the original unplasticized cellulose derivative. Thus a blank for any cellulose derivative is 100. Most of the common plasticizers at 15 per cent concentration produce cellulose derivative compositions having a hardness index ranging from 35 to about '75. The plasticizers of the present invention in like concentration yield. compositions whose hardness indexis at least 90 and'in many instances is as high as 135 to 140. The surprising feature is that the hardness of the cellulose derivative is not only retained or im provedbut that the tensile strength of the composition is not materially reduced.

The hardness index of cellulose derivative compositions is an especially desirable property to keep inmind when selecting extrusion coating compositions such as those employed in the preparation of insulated electric Wire. The hardness index may be considered an index of the resistance of the extruded coating to abrasion. When a composition has both high hardness index and good flexibility rating accompanied by suitabletensile strength and elongation properties, the composition may be employed underthe strenuous conditions to which coated wire is subjected. Because of the unusual retention of hardness resulting from the introduction of the herein-described plasticizer, the compositions of the present invention are particularly adapted foruse as molding and. extrusion plastics;

The followingtables set forth briefly a few of the properties of, some of the poly-halogenated diphenyloxide derivatives which we have found satisfactory for the present purpose and the properties of some ethyl cellulose compositions wherein these compounds were employed as plasticizers.

Table I l No. Plasticizer name Boiling range Refractive index Physical form 1 i l l. Tetrabromo mono chloro di 239267 C. at 7 mm 1. 6615. u. Light yellow liquid.

phenyloxide. 1 I 2 Pentabromo-diphenyloxlde 4 int-$2 C. at 7 mm 1.6695 at 50 C. Viscous yellow liquid. 3 Tetrabromomhenyl diphenyld 1.6754 Very viscous, light 3 91' oxide. low, clear liquid. 4 Hexabromo phenyl diphenyl- ,1. 661i Yellow resin.

oxide-Batch 619. 5 Hexabromo-diphenyloxide.. 267-29? C. at 16 mm 1. 7-. .s Do. 6 Hexabromo -phenyl d1phenyl- 320 at 8 mm, 340 at 9 mm..." 1.661 .7 Do.

oxide- Batch 692. 1

Table II 100 ethyl cellulose, 15 plasticizer 100 ethyl cellulose, 40 plasticiier P111513 Y cizer 0. er Per Yield Tensile cent Yield Tensile cent point strength elgicirglaifldex point strength elegglglaindex:

460 720 41 97 340 1 520 450 700 40 95 395 550 535 700 32 112 540' 600 650' 650 12 137 760' 760 520 695 32 110 .505 520. 6 575 685 28 -l21 l 675' Blank 475 650 34' 100 ,475 650 harder than is ethyl cellulose.

jindex of, the compositions containing .15

shown in the following table plasticized with the common well known plasticizers diphenylphthalate, tricresyl-phosphate, dibutyl-phthalate and castor oil.

equivalent or such s tatem'ingr'edints a -en ployed. q We therefoe particularly point out and distinctly claim as ourdnyention:

l. A molding ,compositibnpomprisi hg a cellu- T In wherein Y is a member of the class consisting of Table' III 100 ethyl cellulose, 15 plasticizer 100 ethyl cellulose, 40 plasticizert m Yield Tensile Elonga- Hard- Yield Tensile Elonga Hsapoint, strength, tron, ness point, strength, tion, ness kgJcm. kg/em. percent index kgJcm. kg./cm. percent index Diphenyl-phthalate 380 l 535 35 so 170 254 48 36 Tricresylhosphate 320 525 46 67 100 130 36 21 Drbutylp thalate 270 390 35 57 82 82 24 17 Castor o1l .l 360 580 45 76 95 168 50 20 The same type of results, in general, are obtained when other cellulose derivatives are plasticized with the herein-described plasticizers, it

being remembered that, with the exception of benzyl cellulose, which is softer, most of the commercial cellulose derivatives are all inherently lustrated in the following table which shows the relative yieldpoint hardness of severalcellulose derivatives, computed on the basis that the ethyl cellulose had a hardness value of 100. Nitro-cellulose, 6 sec. R. S. 167 Cellulose acetate 30-40 sec. high acetyl 147 Cellulose aceto-butyrate, medium viscosity 140 Cellulose aceto-propionatel 139 Ethyl cellulose 48.5% ethoxyl, centipoises 100 Benzyl cellulose, medium viscosity 86 Per cent Ethyl cellulose 49% ethoxyl, 255 centipoise viscosity 48.8 Tetrabromo-diphenyloxide 48.8 Ceresin wax 2.0 Pigment; 0.4 The composition was prepared without solvent by colloiding the ingredients together in a steamheated mixer at a steam pressure of 60 lbs. per square inch. The mixture was fused and extruded onto wire in the customary manner. The coating was found to have good adherence to the wire and to provide a highly flexible insulation which not only had satisfactory dielectric properties but which possessed fairly high flame resistance,--an important attribute of insulated wires to be used around motors where arcing is apt to occur.

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the materials employed, provided the ingredients stated by any of the following claims or the This point is ilor circuit breakers the phenyl group and hydrogen, X is at least one of the halogens,--chlorine and bromine, and n is a numeral from I to 3. r

2. A composition of matter consisting of a cellulose derivative plasticized with about 15 parts, per 100 parts of the cellulose derivative, of at least one compound having the general formula of the phenyl group and hydrogen; X is at least one of the halogens,-chlorine and bromine, and

n is a numeral from 1 to having a hardness at least 90 per cent that of the cellulose derivative alone. l

3. A composition of matter lulose ether and from 5 to 40 of the cellulose ether of at having the formula comprising a celparts, per parts least one compound wherein Y is amember of the class consisting of 3, said composition the phenyl group and hydrogen, X is at least one of the halogens-chlorine and bromine, andn is a numeral from 1 to 3.

.4. A composition of matter comprising a cellulose ester and from 5 to 40 parts, per 100 parts of the cellulose ester, of at least one compound having the general formula n is a numeral from 1 to 3.

5. A composition of matter comprising ethyl cellulose and from 5 to 40 parts, per 100 parts of the ethyl cellulose, of at least one compound having the general formula wherein Y is a member of the class consisting of the phenyl group and hydrogen, X is at least one of the halogens chlorine and bromine, and n is a numeral from 1 to 3.

SHAILER L. BASS. EDGAR C. BRIT'ION. 

